/*
 * Copyright (C) 2010 The MobileSecurePay Project
 * All right reserved.
 * author: shiqun.shi@alipay.com
 */

package com.aier.user.action.pay.alipay.util;

import com.aier.common.common.Constant;

public final class Base64 {

    private static final int     BASELENGTH           = 128;
    private static final int     LOOKUPLENGTH         = 64;
    private static final int     TWENTYFOURBITGROUP   = 24;
    private static final int     EIGHTBIT             = 8;
    private static final int     SIXTEENBIT           = 16;
    private static final int     FOURBYTE             = 4;
    private static final int     SIGN                 = -128;
    private static final char    PAD                  = '=';
    private static final boolean fDebug               = false;
    private static final byte[]  base64Alphabet       = new byte[BASELENGTH];
    private static final char[]  lookUpBase64Alphabet = new char[LOOKUPLENGTH];

    static {
        for (int i = 0; i < BASELENGTH; ++i) {
            base64Alphabet[i] = -1;
        }
        for (int i = 'Z'; i >= 'A'; i--) {
            base64Alphabet[i] = (byte) (i - 'A');
        }
        for (int i = 'z'; i >= 'a'; i--) {
            base64Alphabet[i] = (byte) (i - 'a' + Constant.num_26);
        }

        for (int i = '9'; i >= '0'; i--) {
            base64Alphabet[i] = (byte) (i - '0' + Constant.num_52);
        }

        base64Alphabet['+'] = Constant.num_62;
        base64Alphabet['/'] = Constant.num_63;

        for (int i = 0; i <= Constant.num_25; i++) {
            lookUpBase64Alphabet[i] = (char) ('A' + i);
        }

        for (int i = Constant.num_26, j = 0; i <= Constant.num_51; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('a' + j);
        }

        for (int i = Constant.num_52, j = 0; i <= Constant.num_61; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('0' + j);
        }
        lookUpBase64Alphabet[Constant.num_62] = '+';
        lookUpBase64Alphabet[Constant.num_63] = '/';

    }

    private static boolean isWhiteSpace(char octect) {
        return octect == Constant.num_0x20 || octect == Constant.num_0xd || octect == Constant.num_0xa || octect == Constant.num_0x9;
    }

    private static boolean isPad(char octect) {
        return octect == PAD;
    }

    private static boolean isData(char octect) {
        return octect < BASELENGTH && base64Alphabet[octect] != -1;
    }

    /**
     * Encodes hex octects into Base64
     *
     * @param binaryData Array containing binaryData
     * @return Encoded Base64 array
     */
    public static String encode(byte[] binaryData) {

        if (binaryData == null) {
            return null;
        }

        int lengthDataBits = binaryData.length * EIGHTBIT;
        if (lengthDataBits == 0) {
            return "";
        }

        int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
        int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
        int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
        char[] encodedData = null;

        encodedData = new char[numberQuartet * Constant.num_4];

        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

        int encodedIndex = 0;
        int dataIndex = 0;
        if (fDebug) {
            System.out.println("number of triplets = " + numberTriplets);
        }

        for (int i = 0; i < numberTriplets; i++) {
            b1 = binaryData[dataIndex++];
            b2 = binaryData[dataIndex++];
            b3 = binaryData[dataIndex++];

            if (fDebug) {
                System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
            }

            l = (byte) (b2 & Constant.num_0x0f);
            k = (byte) (b1 & Constant.num_0x03);

            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (b1 >> 2 ^ Constant.num_0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >>  Constant.num_4) : (byte) (b2 >> Constant.num_4 ^ Constant.num_0xf0);
            byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >>  Constant.num_6) : (byte) (b3 >> Constant.num_6 ^ Constant.num_0xfc);

            if (fDebug) {
                System.out.println("val2 = " + val2);
                System.out.println("k4   = " + (k << Constant.num_4));
                System.out.println("vak  = " + (val2 | (k << Constant.num_4)));
            }

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << Constant.num_4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & Constant.num_0x3f];
        }

        // form integral number of 6-bit groups
        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & Constant.num_0x03);
            if (fDebug) {
                System.out.println("b1=" + b1);
                System.out.println("b1<<2 = " + (b1 >> 2));
            }
            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (b1 >> 2 ^  Constant.num_0xc0);
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[k << Constant.num_4];
            encodedData[encodedIndex++] = PAD;
            encodedData[encodedIndex++] = PAD;
        } else if (fewerThan24bits == SIXTEENBIT) {
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            l = (byte) (b2 & Constant.num_0x0f);
            k = (byte) (b1 & Constant.num_0x03);

            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (b1 >> 2 ^  Constant.num_0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> Constant.num_4) : (byte) (b2 >>  Constant.num_4 ^  Constant.num_0xf0);

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << Constant.num_4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
            encodedData[encodedIndex++] = PAD;
        }

        return new String(encodedData);
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param encoded string containing Base64 data
     * @return Array containind decoded data.
     */
    public static byte[] decode(String encoded) {

        if (encoded == null) {
            return null;
        }

        char[] base64Data = encoded.toCharArray();
        // remove white spaces
        int len = removeWhiteSpace(base64Data);

        if (len % FOURBYTE != 0) {
            return null;//should be divisible by four
        }

        int numberQuadruple = len / FOURBYTE;

        if (numberQuadruple == 0) {
            return new byte[0];
        }

        byte[] decodedData = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

        int i = 0;
        int encodedIndex = 0;
        int dataIndex = 0;
        decodedData = new byte[numberQuadruple * Constant.num_3];

        for (; i < numberQuadruple - 1; i++) {
            d1 = base64Data[dataIndex++];
            d2 = base64Data[dataIndex++];
            d3 = base64Data[dataIndex++];
            d4 = base64Data[dataIndex++];
            if (!isData(d1) || !isData(d2)
                || !isData(d3)
                || !isData(d4)) {
                return null;
            }//if found "no data" just return null

            b1 = base64Alphabet[d1];
            b2 = base64Alphabet[d2];
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];

            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> Constant.num_4);
            decodedData[encodedIndex++] = (byte) (((b2 & Constant.num_0xf) << Constant.num_4) | ((b3 >> 2) & Constant.num_0xf));
            decodedData[encodedIndex++] = (byte) (b3 << Constant.num_6 | b4);
        }
        
        d1 = base64Data[dataIndex++];
        d2 = base64Data[dataIndex++];
        if (!isData(d1) || !isData(d2)) {
            return null;//if found "no data" just return null
        }

        b1 = base64Alphabet[d1];
        b2 = base64Alphabet[d2];

        d3 = base64Data[dataIndex++];
        d4 = base64Data[dataIndex++];
        if (!isData(d3) || !isData(d4)) {//Check if they are PAD characters
            if (isPad(d3) && isPad(d4)) {
                if ((b2 & Constant.num_0xf) != 0)//last 4 bits should be zero
                {
                    return null;
                }
                byte[] tmp = new byte[i * Constant.num_3 + 1];
                System.arraycopy(decodedData, 0, tmp, 0, i * Constant.num_3);
                tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> Constant.num_4);
                return tmp;
            } else if (!isPad(d3) && isPad(d4)) {
                b3 = base64Alphabet[d3];
                if ((b3 & Constant.num_0x3) != 0)//last 2 bits should be zero
                {
                    return null;
                }
                byte[] tmp = new byte[i * Constant.num_3 + 2];
                System.arraycopy(decodedData, 0, tmp, 0, i * Constant.num_3);
                tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> Constant.num_4);
                tmp[encodedIndex] = (byte) (((b2 & Constant.num_0xf) << Constant.num_4) | ((b3 >> 2) & Constant.num_0xf));
                return tmp;
            } else {
                return null;
            }
        } else { //No PAD e.g 3cQl
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> Constant.num_4);
            decodedData[encodedIndex++] = (byte) (((b2 & Constant.num_0xf) << Constant.num_4) | ((b3 >> 2) & Constant.num_0xf));
            decodedData[encodedIndex++] = (byte) (b3 << Constant.num_6 | b4);

        }

        return decodedData;
    }

    /**
     * remove WhiteSpace from MIME containing encoded Base64 data.
     *
     * @param data  the byte array of base64 data (with WS)
     * @return      the new length
     */
    private static int removeWhiteSpace(char[] data) {
        if (data == null) {
            return 0;
        }

        // count characters that's not whitespace
        int newSize = 0;
        int len = data.length;
        for (int i = 0; i < len; i++) {
            if (!isWhiteSpace(data[i])) {
                data[newSize++] = data[i];
            }
        }
        return newSize;
    }
}
